This invention relates to lighting fixtures and systems, and particularly to lighting systems for lighting work areas under cabinets or on and around desk surfaces in offices and the like.
From the standpoint of pleasing appearance as well as good lighting of work areas, ceiling and wall fixtures in business offices, factories and homes are rapidly being replaced by lighting fixtures which are mounted on or integrated into cabinets, bookshelves, and facia panels of various types. Such constructions bring the light source closer to the task and reduce or eliminate direct glare by hiding the light source from view and by controlling the light with suitable lenses, refractors, reflectors, baffles, louvers and the like. The light can thereby be directed downwardly and upwardly, the latter if lighting of the immediate environment above the work area is also required. When incorporated into office partitions, such lighting fixtures readily adapt to almost any work area. Systems of the foregoing types are described in applicant's U.S. Pat. No. 3,389,246, issued June 18, 1968.
Refractor plates of specialized design are now available which will reduce or eliminate both direct and reflected glare from a light source. Reflected glare is also known as veiling reflection and results from reflections from a task and the background of the task. For example, light-colored desk surfaces, writing paper thereon and light colored backgrounds reflect desirable light, but if the task (e.g., pencil writing) also reflects light to the viewer, the contrast between the task and its immediate background is reduced. It is this reduction of contrast which makes seeing difficult.
Direct glare can be eliminated by baffles, shields, refractors and reflectors which cut off direct view of the lighting source. As for the elimination of veiling reflections, when their source is light emitted downward from a zone located above and slightly in front of the task area, refractor plates have been developed which refract or redirect the light. This refraction can be visualized in terms of the photometric curves showing relative candlepower distribution of the luminous flux. These curves take the form of a half bat wing shape, or a full bat wing shape if all of the luminous flux below and adjacent to the plane of the refractor is analyzed. The bat wing configurations represent luminous flux patterns and indicate the direction and distribution of the flux.
Typical of refractor plates which distribute luminous flux from a light source in a bat wing configuration are the plates described in U.S. Pat. No. 3,258,590 -- Goodbar and the commercially available refractor plate known as "K-S-H 701 Lensmatic" lens, K-S-H, Inc., St. Louis, Missouri. While such refractor plates are known to distribute light in the useful bat wing configuration, their use has been defective in that they have not been task oriented, thereby resulting in direct glare and veiling reflections.